The applicant of the present patent application has a prior utility model application in China titled “Reciprocal Motor Tricycle”, which discloses a reciprocal motor tricycle. The reciprocal motor tricycle includes a damping mechanism hinged between the lower rocker and the balance plate and the balance plate can rotate left and right relative to the frame through the hollow shaft at the bottom thereof, so that the frame is not limited by the damping mechanism and is capable of being tilted left and right at a large scale. As a result, sufficient positive pressure can be produced between the inner wheel of the vehicle and the ground so as to balance the centrifugal force on the vehicle and thereby effectively improve the anti-rollover capability of the vehicle during turns. However, when the reciprocal motor tricycle is running straightly on a road with bad conditions, because the frame is always in a swinging mode, when the ups and downs are frequent, the frame of the reciprocal motor tricycle will be hard to be kept in balance and swing left and right easily. As a result, the driver riding on the motor tricycle may fall off from the vehicle because of the unstable center of mass, so that the personal safety of the driver will be jeopardized.